Method of back-side patterning

Abstract

A method of back-side patterning of a silicon wafer is disclosed, which includes: depositing a protective layer on a front side of a silicon wafer; forming one or more deep trenches through the protective layer and extending into the silicon wafer by a depth greater than a target thickness of the silicon wafer; flipping over the silicon wafer and bonding the front side of the silicon wafer with a carrier wafer; polishing a back side of the silicon wafer; performing alignment by using the one or more deep trench alignment marks and performing back-side patterning process on the back side of the silicon wafer; and de-bonding the silicon wafer with the carrier wafer.

What is claimed is: 
     
       1. A method of back-side patterning, comprising the following steps in the sequence set forth:
 depositing a protective layer on a front side of a silicon wafer; 
 forming, on the front side of the silicon wafer, one or more deep trenches to serve as one or more deep trench alignment marks for back-side patterning, the one or more deep trenches being formed through the protective layer and extending into the silicon wafer, each of the one or more deep trenches extending into the silicon wafer by a depth greater than a target thickness of the silicon wafer and being not filled with any material so that the one or more deep trench alignment marks remain hollow; 
 flipping over the silicon wafer and bonding the front side of the silicon wafer with a carrier wafer; 
 polishing a back side of the silicon wafer by using Taiko polishing process until a thickness of a central portion of the silicon wafer is reduced to the target thickness and the one or more hollow deep trench alignment marks are exposed from the back side of the silicon wafer, such that a support ring having a thickness greater than the thickness of the central portion of the silicon wafer is formed at an edge portion of the silicon wafer; 
 performing alignment by using the one or more hollow deep trench alignment marks and performing back-side patterning process on the back side of the silicon wafer; 
 de-bonding the silicon wafer with the carrier wafer; and 
 removing the support ring. 
 
     
     
       2. The method according to  claim 1 , further comprising performing front-side patterning process on the front side of the silicon wafer before depositing a protective layer on the front side of the silicon wafer. 
     
     
       3. The method according to  claim 2 , wherein the front-side patterning process comprises a front-side forming process and a front-side interconnecting process. 
     
     
       4. The method according to  claim 2 , wherein at least part of the back-side patterning process is performed by using same devices and process conditions with the front-side patterning process. 
     
     
       5. The method according to  claim 1 , wherein the carrier wafer is made of glass, ceramic or sapphire. 
     
     
       6. The method according to  claim 1 , wherein the protective layer has a thickness of 3000 Å to 50 μm. 
     
     
       7. The method according to  claim 6 , wherein the protective layer has a thickness of 1 μm to 10 μm. 
     
     
       8. The method according to  claim 1 , wherein the protective layer is selected from a multilayer of silicon dioxide, silicon nitride, silicon oxynitride, silicon dioxide and silicon nitride, a multilayer of silicon dioxide, silicon nitride and silicon oxynitride, or a compound of silicon, oxygen, carbon and nitrogen. 
     
     
       9. The method according to  claim 1 , wherein de-bonding the silicon wafer with the carrier wafer is performed by using laser irradiation, chemical dissolution or thermal decomposition. 
     
     
       10. The method according to  claim 1 , further comprises removing the protective layer after de-bonding the silicon wafer with the carrier wafer. 
     
     
       11. A method of back-side patterning, comprises the following steps in the sequence set forth:
 depositing a protective layer on a front side of a silicon wafer; 
 forming, on the front side of the silicone wafer, one or more deep trenches to serve as one or more deep trench alignment marks for back-side patterning, the one or more deep trenches being formed through the protective layer and extending into the silicone wafer, each of the one or more deep trenches extending into the silicon wafer by a depth greater than a target thickness of the silicon wafer; 
 filling the one or more deep trenches with silicon dioxide; 
 flipping over the silicon wafer and bonding the front side of the silicon wafer with a carrier wafer; 
 polishing a back side of the silicon wafer by using Taiko polishing process until a thickness of a central portion of the silicon wafer is reduced to the target thickness and the one or more deep trench alignment marks are exposed from the back side of the silicon wafer, such that a support ring having a thickness greater than the thickness of the central portion of the silicon wafer is formed at an edge portion of the silicon wafer; 
 performing a hydrofluoric acid liquid based wet etching process to the silicon dioxide filled in the one or more deep trenches to make a level of a surface of the silicon dioxide more than 500 Å lower than a level of surface of the central portion of the silicon wafer; 
 performing alignment by using the one or more deep trench alignment marks and performing back-side patterning process on the back side of the silicon wafer; 
 de-bonding the silicon wafer with the carrier wafer; and 
 removing the support ring.